Author: Tony Werten
Date: 13:15:34 01/10/03
Go up one level in this thread
On January 10, 2003 at 15:37:03, Uri Blass wrote:
>On January 10, 2003 at 15:31:05, Bas Hamstra wrote:
>
>>Hi Uri,
>>
>>Personally I use a lookup table for 8 bits at a time (count each row). You can
>>see a bitboard as an array of 8 unsigned chars.
>>
>>BB Test = 423434234ui64;
>>int Count = PopCnt(Test);
>>
>>inline int PopCnt(BB BitBoard)
>>
>>{ unsigned char* p = (unsigned char*) BitBoard;
>> return PopCnt8[p[0]] + PopCnt8[p[1]] ... + PopCnt8[p[7]];
>>}
>>
>>You have to create an small precalculated array PopCnt8[256] for this. It is not
>>the absolute fastest, but also not much slower than that.
>>
>>Bas.
>
>Thasks but I have already that array for other purpose so I do not need to
>create it.
>
>I simply thought that if there is a simple way to do things faster I can do it.
>I want to use it to calculate the number of protected passed pawns because as
>first step I plan to give a static bonus for passed pawn that is protected by a
>pawn(I may change it later to something better but passed pawn that is protected
>by a pawn is usually good not like other passed pawns that may be often bad).
>
>I admit that in this case I can add only 5 numbers because protected passed pawn
>cannot be in the first second or last rank so maybe your idea is faster.
To count protected passed pawns the fasted way is probably
count:=0;
while bitboard<>0 do
begin
inc(count)
bitboard:=board and (bitboard-1)
end
Tony
>
>Uri
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